Sputtering equipment that is used to manufacture semiconductors and other data processing and storage devices includes one or more vacuum processing chambers in which a substrate is supported for processing. For sputter coating processes, a target of sputter coating material from which material is sputtered is placed in the chamber, in which a plasma is created to supply ions of gas which sputter the material from the target. While the objective is to form a film on the substrate of the sputtered material, material also coats the surfaces of chamber walls and other structures in contact with the volume of the chamber. These coatings must be periodically removed or they will eventually flake off and contaminate substrates being processed in the chamber or interfere with the operation of the equipment.
Cleaning of the fixed components of the processing chamber is time consuming, requiring the equipment to be shut down, and subtracting from the productivity of the equipment. To minimize these shut-downs, removable shields are provided in the chamber to intercept coating material from alighting on the walls and other chamber components. These shields can be removed and replaced, or cleaned and reused, thereby enabling the machines to be returned to production in less time. Such shields can be fabricated from different materials, and are often made of aluminum or stainless steel.
The complicated structure of processing chambers has resulted in the chamber shields being made in a number of parts. Process considerations such as coating film uniformity on the substrate and process parameters such as gas flow, electric and magnetic field shapes and sputtering geometry have affected the designs of the individual shield components. As a result, the number and shapes of the chamber shields have added to the removal and replacement times for the shields and limited the productivity savings that the shields provide. In addition to contributing to the down-time of the machine that is needed to change chamber shields, replacements for complex shield systems are expensive and, in addition to the loss of valuable production time, add to the machine's maintenance costs.
High speed processing machines such as those of the vertical, split-plenum type, in which the processing chambers are formed in two halves on opposite sides of a rotating, index-wheel or index-plate, multiple-wafer holder, impose additional difficulties on the designs of chamber shields. The complexities that result from the configuration of these machines is apparent from the designs of these chambers, as illustrated, for example, in FIGS. 1, 17-19 and 22 of U.S. Pat. No.4,915,564; FIGS. 1 and 3 of U.S. Pat. No. 5,820,329; and FIG. 5 of U.S. Pat. No. 6,258,228, which are incorporated by reference above.
The index wheel or plate of the machines described in these patents includes typically five wafer holders spaced at equal angular intervals around the center of the index plate, which rotates in a vertical plane around a horizontal axis through the center of the plate. The rotation of the plate indexes the wafer holders among five stations, one of which is a load lock and the other four of which are processing stations. Typically three of these stations include sputter deposition chambers. Another of the chambers is typically a sputter etch chamber. The chambers are formed by the movement toward each other of a pair of cup-shaped members that clamp against a seal ring in the center of which a wafer holder is mounted, and form a split processing chamber on the opposite sides of the wafer holder. The stations of the machine at which the processing chambers are so formed are referred to as pods. Each of the pods that contain one of the processing chambers is provided with a chamber shield system.
FIG. 2 of the present application illustrates approximately a dozen shield components of a prior art shield system required to shield each sputter coating chamber of the apparatus described in the patents referred to above. FIGS. 3, 3A and 3B are cross-sectional views of a two-part funnel-shaped prior art shield that has been used to replace the wafer-holder shield and other components of the shield system of FIG. 2, reducing the total number of shield components.
There remains a need to improve the chamber shielding in vertical split-plenum type processing machines, to reduce the cost of the replaceable chamber shields for such machines, and to shorten the time needed to replace the chamber shields.